EP1375626A2 - Lumineszenzmittel, pulverförmiges Lumineszenzmittel, Plasma-Anzeigetafel, und Herstellungsverfahren derselben - Google Patents

Lumineszenzmittel, pulverförmiges Lumineszenzmittel, Plasma-Anzeigetafel, und Herstellungsverfahren derselben Download PDF

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Publication number: EP1375626A2
Authority: EP; European Patent Office
Prior art keywords: phosphor; particles; plasma display; display panel; luminance
Prior art date: 1997-11-06
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.): Granted

Application number

EP03020149A

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English (en)

French (fr)

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EP1375626A3 (de

EP1375626B1 (de

Inventor

Masaki Aoki

Hiroyuki Kado

Shigeo Suzuki

Hiroyuki Kawamura

Mitsuhiro Ohtani

Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

Panasonic Holdings Corp

Original Assignee

Matsushita Electric Industrial Co Ltd

Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)

1997-11-06

Filing date

1998-11-05

Publication date

2004-01-02

1997-11-06 Priority claimed from JP9304184A external-priority patent/JPH11144625A/ja

1997-12-05 Priority claimed from JP9335353A external-priority patent/JPH11166178A/ja

1997-12-17 Priority claimed from JP9347465A external-priority patent/JPH11172241A/ja

1998-03-04 Priority claimed from JP05172298A external-priority patent/JP3161409B2/ja

1998-05-15 Priority claimed from JP13298398A external-priority patent/JP3185752B2/ja

1998-07-08 Priority claimed from JP19300098A external-priority patent/JP3202964B2/ja

1998-11-05 Application filed by Matsushita Electric Industrial Co Ltd filed Critical Matsushita Electric Industrial Co Ltd

2004-01-02 Publication of EP1375626A2 publication Critical patent/EP1375626A2/de

2004-02-18 Publication of EP1375626A3 publication Critical patent/EP1375626A3/de

2007-04-04 Publication of EP1375626B1 publication Critical patent/EP1375626B1/de

2007-04-04 Application granted granted Critical

2018-11-05 Anticipated expiration legal-status Critical

Status Expired - Lifetime legal-status Critical Current

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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
- C09K11/7728—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing europium
- C09K11/7734—Aluminates
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2211/00—Plasma display panels with alternate current induction of the discharge, e.g. AC-PDPs
- H01J2211/20—Constructional details
- H01J2211/34—Vessels, containers or parts thereof, e.g. substrates
- H01J2211/42—Fluorescent layers

Definitions

the present invention relates to a phosphor material and a phosphor material powder that emit light with a high efficiency, a plasma display panel used in display devices and a method of producing the same.
the CRT has been commonly used as the display device for television sets.
the CRT although better in resolution and picture quality than the plasma display panel and the liquid crystal display, is not suited to large screens having diagonal size of 40 inches or more for the reason of depth size and weight.
the liquid crystal display is limited in the screen size and the viewing angle, in spite of such advantages as the low power consumption and low drive voltage.
the plasma display panel can be used in a large-screen display because there is no problem of depth size and weight, and 40-inch class products using the plasma display panel have already been developed (for example, see Functional Materials, February issue, 1996, Vol. 16, pp. 2, 7).
Fig. 23 is a sectional view showing schematic constitution of the AC type plasma display panel.
numeral 41 denotes a front cover plate (front glass substrate) with a display electrode 42 formed on the front glass substrate 41.
the front cover plate 41 with the display electrode 42 formed thereon is also covered by a dielectric glass layer 43 and a protective layer 44 made of magnesium oxide (MgO) (see, for example, Unexamined Patent Publication (Kokai) No. 5-342991).
MgO magnesium oxide
Numeral 45 denotes a back plate (back glass substrate), with an address electrode 46, barrier rib 47 and spherical phosphor layer 48 being provided on the back glass substrate 45, and numeral 49 denotes an electric discharge space filled with a discharge gas.
the phosphor layer comprises phosphor layers of three colors, red, green and blue, disposed in this order for color display. The phosphor layers of different colors are excited to emit light by ultraviolet rays of short wavelength (147 nm) emitted by electric discharge.
(YGd)BO 3 : Eu is used for red
BaMgAl 10 O 17 : Eu is used for blue
Zn 2 SiO 4 :Mn is used for green today (for example, Electronics Packaging Technology; July, 1997; Vol. 113, No. 7, pp. 23-26).
the plasma display panels of 40- to 42-inch class described above that are produced at present have luminance of 150 to 250 cd/m 2 at the pixel level of NTSC (640 ⁇ 480 pixels, cell pitch 0.43 mm ⁇ 1.29 mm, area of one cell 0.55 mm 2 ) (for example, refer to Functional Materials, February issue, 1996, Vol. 16, pp. 2, 7).
plasma display panels of 40- to 42-inch class having luminance of 250 to 450 cd/m 2 at the pixel level of NTSC have also been reported (for example, see Flat Panel Display, 1997, Part 5-1, pp. 198-199).
the conventional CRT technology is said, by contrast, to be capable of achieving a luminance of about 500 cd/m 2 .
screen area per one pixel become as small as 1/7 to 1/8 that of the NTSC display.
emission intensity of the display panel becomes 1/7 to 1/8 that of the NTSC display, namely 0.15 to 0.171 m/W.
luminance of a high-definition television produced with the 42-inch plasma display panel is predicted to be as low as 30 to 40 cd/m 2 , given the same phosphor, gas composition and gas pressure, making it desirable to improve the luminance.
the first problem is that phosphor materials of different colors have different levels of luminance.
green phosphor While several types of phosphor have been investigated for each of red, green and blue light in the plasma display panel, green phosphor has the highest luminance and blue phosphor has the lowest luminance in any of these types.
luminance ratio of the colors of red, green and blue is about 2: 3: 1, with a low color temperature of about 5000 degrees.
phosphor layers of the plasma display panels of the prior art are formed by applying an ink that contains phosphor particles by a printing process or coating a photosensitive sheet that contains phosphor particles.
the phosphors used in the panel are subject to a certain extent of thermal change that results in degradation of luminance and/or chromaticity.
the plasma display panel has the problem of the thermal deterioration of the phosphor material in the firing process that are required for the production (for example, Transaction of the 263rd Conference of Phosphor Engineering Association, pp. 9-13, 1996; Optonics, 1997, No.6, pp. 149-155).
the phosphors are subject to a certain extent of thermal change that results in degradation of luminance and/or chromaticity.
the Ba (1-x) MgAl 10 O 17 :Eu x used as the blue phosphor can easily be damaged by vacuum ultraviolet rays (wavelength 147 nm, 172 nm) that excite the plasma display panel, and the emission intensity decreases as the panel is operated longer, thus giving rise to a problem of service life.
the blue phosphor material of the plasma display panel has the problems of thermal deterioration of the phosphor material in the firing processes required for the producing and short service life.
First object of the present invention is to provide a phosphor material and a phosphor material powder of high luminance, particularly a phosphor material and a phosphor material powder that are suited to a plasma display panel and a method of producing the same.
Second object of the present invention is to provide a plasma display panel having high luminance and high reliability.
the first plasma display panel of the present invention has, for the purpose of achieving the first object described above, a plurality of discharge spaces formed between a front panel and a back panel that are disposed to oppose each other, and phosphor layers, formed in the discharge spaces, each including phosphor particles of one of blue, red and green colors, wherein the phosphor particles of at least one of blue, red and green colors included in the phosphor layer are flake-like particles.
Phosphors used in the plasma display panel of the prior art have generally made by firing for a long period of time at high temperatures (for example, 1200°C though the firing temperature depends on the composition of the phosphor) at which crystals are likely to grow into spherical shape.
the phosphor particles used in the plasma display panel of the prior art have been of near spherical shape having large diameters (about 5 to 10 ⁇ m) .
Such phosphor particles of near spherical shape have been advantageous in transmission type devices such as CRT and fluorescent lamp where visible light must be transmitted between the phosphor particles.
Coverage ratio in this specification refers to an index that represents the proportion of the surface of the walls covered by the phosphor material or the phosphor particles to the total area of wall surface whereon the phosphor layer is formed. As the coverage ratio increases, higher proportion of the light incident on the phosphor layer is absorbed by the phosphor material and the phosphor particles.
the barrier ribs and the base in the phosphor layer are covered by the phosphor particles with higher coverage ratio, which increases the proportion of ultraviolet rays absorbed in the phosphor layer.
higher luminance than the prior art can be achieved in the first plasma display panel of the present invention.
the constitution of the present invention that increases the percentage of loading and coverage ratio of the phosphor layer with the phosphor particles is very effective in absorbing much of the ultraviolet rays in the superficial portion of the phosphor layer.
the percentage of loading and coverage ratio of the phosphor layer with the phosphor particles can be increased in the first plasma display panel of the present invention, emission intensity of the phosphor layer can be increased.
the phosphor particles themselves act as reflectors for visible light increasing the percentage of loading by phosphor increases the luminance of reflection at the same time. This effect is made conspicuous when the flaky phosphor particles are used in the phosphor layers of every color.
the phosphor layers that include the flaky phosphor particles are formed, efficiency of absorbing ultraviolet rays in the phosphor layer can be increased and thereby increasing the luminance of the plasma display panel.
Such flaky phosphor particles as described above can be easily made changing the firing conditions, starting materials or atmosphere of firing when making the phosphor. Specifically, phosphor particles that have better crystallizability in the very superficial portion of the phosphor layer and a higher profile ratio (breadth/thickness) can be obtained by setting the firing temperature somewhat higher and performing the firing for a shorter period of time.
Blue and green phosphor particles can be relatively easily made in a shape of hexagonal flake because these substances have hexagonal system of crystalline structure (see, for example, Phosphor Handbook, Ohm Publishing Co., pp. 219, pp. 225). Red phosphor particles, however, have cubic system and are therefore difficult to make in flaky shape. However, it becomes relatively easy to make red phosphor particles of flaky shape by using yttrium hydroxide (Y 2 (OH) 3 ) as the starting material.
Y 2 (OH) 3 yttrium hydroxide
the first plasma display panel of the present invention it is preferable for the first plasma display panel of the present invention, according to our study, to set the breadth and thickness of the flakes of phosphor particles as follows, although it depends on the color.
the blue phosphor particles described above may comprise flaky particles based on a phosphor represented by general formula ofBa (1-x) Eu x MgAl 10 O 17 (0 03 ⁇ x ⁇ 0. 25) as the major component, while preferably the breadth thereof is in a range from 0.3 to 6 ⁇ m, thickness is in a range from 0.1 to 2 ⁇ m, and profile ratio (breadth/thickness) is in a range from 3 to 25.
the phosphor represented by the general formula Ba (1- x) Eu x MgAl 10 O 17 is a phosphor represented by BaMgAl 10 O 17 Eu 2+ .
the green phosphor particles may comprise flaky particles made of a phosphor represented by a general formula of (Zn 1- x Mn x )SiO 4 . (0.01 ⁇ x ⁇ 0.05) as the major component, while preferably the breadth thereof is in a range from 0.3 to 6 ⁇ m, thickness is in a range from 0.1 to 2 ⁇ m, and profile ratio (breadth/thickness) is in a range from 3 to 25.
the phosphor represented by the general formula Zn 1-x Mn x ) SiO 4 is represented as Zn 2 SiO 4 :Mn 2+ .
the red phosphor particles may comprise flaky particles made of a phosphor represented by a general formula of Y 1-x Eu x BO 3 (0.05 ⁇ x ⁇ 0.15) as the major component, while preferably the breadth thereof is in a range from 0.5 to 6 ⁇ m, thickness is in a range from 0.2 to 2 ⁇ m, and profile ratio (breadth/thickness) is in a range from 2.5 to 15.
the phosphor represented by the general formula Y 1-x Eu x BO 3 is a material represented by YBO 3 : Eu 3+ .
the phosphor particles having a high profile ratio as described above are preferably made by adding a somewhat greater amount of activation agent in order to ensure sufficient number of luminance centers for the amount of ultraviolet rays absorbed.
the discharge space can be formed on the back panel by partitioning the surface with barrier ribs that are formed by plasma spraying.
the phosphor layers can be formed on the barrier ribs and on the bottom surface of the discharge space by firing after continuously discharging the phosphor ink, that includes the phosphor particles, a solvent and a resin binder, from a nozzle and then drying.
the barrier ribs preferably comprise a first layer made of one white material selected from among a group consisting of alumina (Al 2 O 3 ) , spinel (MgO ⁇ Al 2 O 3 ) and zircon (ZrO 2 ) and a second layer made of a black material selected from among a group consisting of chromium oxide (Cr 2 O 3 ), alumina titania (Al 2 O 3 -TiO 3 ) , chromium oxide-cobalt oxide (Cr 2 O 3 -CoO), chromium oxide-manganese oxide (Cr 2 O 3 -MnO 2 ), and chromium oxide-iron oxide (Cr 2 O 3 ) - Fe 2 O 3 )
a plasma display panel of even more higher luminance and higher display contrast can be obtained by using the flaky phosphor particles and coating the area between the barrier ribs that are black-colored on the upper portion (second layer) with the particles by ink jet process (application of the ink by continuously discharging the ink from a fine tube).
a method of producing the first plasma display panel of the present invention is a method of producing a plasma display panel comprising a plurality of discharge spaces formed between the front panel and the back panel disposed to oppose each other, and phosphor layers that are formed in the discharge spaces and include phosphor particles of one of blue, red and green colors, wherein the phosphor layers are formed by spraying the phosphor ink that includes the phosphor particles, the solvent, a resin binder and a dispersion agent from the nozzle.
the viscosity of the phosphor ink within a range from 15 to 1000 centipoise.
the resin binder In the method of producing the first plasma display panel, it is also preferable to use ethyl cellulose or acrylic resin for the resin binder.
a first phosphor material according to the present invention is a blue phosphor material for the plasma display panel, one selected from a group consisting of a phosphor represented by general formula Ba (1-x) Eu x MgA 10 O 17 a phosphor represented by general formula Ba 2(1-x) Eu 2x Mg 2 Al 12 O 22 a phosphor represented by general formula Ba2 (1-x) Eu 2x Mg 4 Al 8 O 18 and a phosphor represented by general formula Ba 3(1-x) Eu 3x Mg 5 Al 18 O 35 , where value of x is limited as 0.01 ⁇ x ⁇ 0.15, and has a laminar structure
the material represented by BaMgAl 10 O 17 : Eu that has been used as the blue phosphor is a laminar compound having ⁇ -alumina structure or magnetoplumbite structure (see, for example, Phosphor Handbook, Ohm Publishing Co., December 15, 1987, pp. 225)
This conventional blue phosphor material has such a crystal structure as a layer including barium (Ba) (R layer) and a layer without barium (Ba) (spinel layer, S layer) are arranged alternately one on another (plate crystal), wherein europium ion (Eu 2+ ) that serves as the luminescence center is substituted at the lattice position of Ba ion (Eu ions are not substituted in the spinel layer).
the present inventors completed the first phosphor material base on the assumption that luminance increases as the layer containing europium ion (Eu 2+ ) that serves as the luminescence center (layer containing Ba) is made in such a crystal system that exists with a high concentration in the ⁇ -alumina structure.
the first phosphor material of the present invention is made in such a composition that the blue phosphor material for the plasma display panel employs a crystal system of ⁇ -alumina or magnetoplumbite structure such as Ba 2 Mg 4 Al 8 O 18 , Ba 3 Mg 5 Al 18 O 35 or Ba 2 Mg 2 Al 12 O 22 as the base material, where there are more layers that include Ba than in the base material based on BaMgAl 10 O 17 : Eu used in the prior art, and improved in the luminance by substituting Ba of these crystals with Eu.
a crystal system of ⁇ -alumina or magnetoplumbite structure such as Ba 2 Mg 4 Al 8 O 18 , Ba 3 Mg 5 Al 18 O 35 or Ba 2 Mg 2 Al 12 O 22 as the base material, where there are more layers that include Ba than in the base material based on BaMgAl 10 O 17 : Eu used in the prior art, and improved in the luminance by substituting Ba of these crystals with Eu.
the second plasma display panel of the present invention has a plurality of discharge spaces formed between the front panel and the back panel disposed to oppose each other, and the phosphor layers that include phosphor particles of one of blue, red and green colors and are formed in the discharge spaces.
the blue phosphor that constitutes the phosphor layer described above is one or more kinds of phosphor selected from a group consisting of a phosphor represented by general formula Ba (1-x) Eu x MgAl 10 O 17 , a phosphor represented by general formula Ba 2(1-x) EU 2x Mg 2 Al 12 O 22 , a phosphor represented by general formula Ba 2(1-x) EU 2x Mg 4 Al 8 O 18 and a phosphor represented by general formula Ba 3(1-x) Eu 3x Mg 5 Al 18 O 35 , with the condition of 0.01 ⁇ x ⁇ 0.1.
the amount of Eu ions serving as the luminescence center that substitute the Ba ions in the Ba layer is usually set around 10 to 15 atomic percent, unlike in the case of the blue phosphor used in the second plasma display panel.
the second plasma display panel of the present invention based on these results, it is intended to prevent thermal deterioration of the blue phosphor in the phosphor firing process by limiting the proportion of the Ba ions that can be substituted with Eu ions within 10 atomic % of the Ba content.
use of the blue phosphor material of the present invention makes it possible to form the phosphor layer of high luminance and high heat resistance, being capable of suppressing thermal deterioration in the firing process during the production of the plasma display panel, and achieve the plasma display panel of high luminance and good picture quality.
the first phosphor material powder according to the present invention includes the phosphor particles and non-fluorescent white particles that have average particle size smaller than the average particle size of the phosphor particles mixed therein.
the phosphor material powder of the prior art comprises only the phosphor particles.
the percentage of loading of phosphor particles in the layer increases as the particle size of the phosphor becomes smaller and, as a result, the effect of reflection in the layer becomes greater thus making it possible to extract the emitted visible light efficiently through the front surface of the layer.
the first phosphor material powder of the present invention When using such a phosphor material made by mixing the phosphor particles and non-fluorescent white particles that have average particle size smaller than the average particle size of the phosphor particles is used as the first phosphor material powder of the present invention, by contrast, efficient emission of light is achieved with phosphor particles of relatively large particle size. Moreover, when a layer is formed, percentage of loading is increased as the voids between the phosphor particles of relatively large particle sizes is filled with the non-fluorescent white particles of relatively small particle sizes, resulting in improved reflectivity in the layer and making it possible to extract the emitted light efficiently through the front surface of the layer.
average particle size of the phosphor particles is preferably in a range from 1.5 ⁇ m to 5 ⁇ m inclusive, and average particle size of the non-fluorescent white particles is preferably 1.5 ⁇ m or smaller. It is also preferable that average particle size of the phosphor particles is twice that of the non-fluorescent white particles or larger.
the percentage of loading can be increased further by making average particle size of the phosphor particles five times or more larger than that of the non-fluorescent white particles.
the coefficient of particle size concentration of the particle size distribution of at least either the phosphor particles or the non-fluorescent white particles not less than 50% within 100%, which makes it possible to effectively fill the voids between the larger phosphor particles with the smaller non-fluorescent white particles.
the percentage of loading can be increased further by setting the coefficients of particle size concentration of the phosphor particles and the non-fluorescent white particles in a range from 80% to 100% inclusive.
total number of the non-fluorescent white particles is preferably less than the total number of the phosphor particles.
the phosphor particles described above may also be a blue phosphor represented by general formula Ba 1-x Eu x MgAl 10 O 17 .
the phosphor particles described above may also be a green phosphor represented by general formula (Zn 1-x Mn x )SiO 4 .
the phosphor particles may be a green phosphor represented by general formula Ba 1-x Mg x Al 12 O 19 .
the phosphor particles may also be a red phosphor represented by general formula Y 1-x Eu x BO 3 .
the phosphor particles may also be a red phosphor represented by general formula Y 1-x-y Gd x EU y BO 3 .
the percentage of loading can also be increased by using the phosphor particles or the non-fluorescent white particles that are spherical or substantially sphere-shaped particles.
the third plasma display panel of the present invention has a plurality of discharge spaces formed between a front panel and a back panel disposed to oppose each other, with a phosphor layer that includes phosphor particles of one of blue, red and green colors being formed in each of the discharge spaces, while the phosphor layers include the first phosphor material powder of the present invention.
the percentage of loading of the phosphor material powder in the phosphor layer can be increased thus giving the layers good reflective characteristics.
thickness of the phosphor layers is preferably in a range from 5 ⁇ m to 50 ⁇ m.
the second phosphor material powder of the present invention is an aggregate of phosphor particles, and is characterized in that the number of phosphor particles having particle sizes not less than the peak particle diameter Dp is less than the number of phosphor particles having particle sizes not greater than the peak particle diameter Dp, with Dp representing the peak particle diameter in the particle size distribution of the phosphor particles.
Conventional phosphor material powder generally has a nearly symmetrical particle size distribution with the peak particle size at the center thereof.
the phosphor layer that includes the phosphor material powder has higher reflecting effect inside the layer when the percentage of loading is higher, thus making it possible to extract the emitted visible light effectively through the front surface of the layer.
the second phosphor material of the present invention is made by reducing the number of relatively large particles in the particle size distribution to achieve the such a particle size distribution as described above, thus making it possible to fill the voids between the phosphor particles with smaller phosphor particles more densely, and extract the emitted visible light efficiently through the front surface of the layer.
the number of phosphor particles having particle sizes not less than peak particle diameter Dp is preferably within 70% of the number of phosphor particles having particle sizes not greater than the peak particle diameter Dp.
the number of phosphor particles having particle sizes not less than the peak particle diameter Dp is more preferably within 50% of the number of phosphor particles having particle sizes not greater than peak particle diameter Dp, which enables it to improve the percentage of loading further.
the second phosphor material powder of the present invention is an aggregate of phosphor particles, and is prepared to have such a particle size distribution as Dmax - Dp is less than Dp - Dmin, with Dp representing the peak particle diameter, Dmin the minimum particle size and Dmax the maximum particle size of the phosphor particles.
the particle size distribution is preferably such as (Dmax - Dp) is less than 0.5 times the value of (Dp - Dmin).
the particle size distribution is preferably such that (Dmax - Dp) is less than 0.3 times the value of (Dp - Dmin) . This enables it to improve the percentage of loading of the phosphor particles further.
peak particle diameter Dp of the particle size distribution of the phosphor particles is preferably from 1.5 ⁇ m to 5 ⁇ m inclusive.
the phosphor particles may also comprise such a phosphor that the phosphor particles emit visible light upon excitation by ultraviolet rays.
the phosphor particles may also comprise blue phosphor material represented by general formula Ba (1-x) Eu x MgAl 10 O 17 .
the phosphor particles may also comprise a green phosphor material represented by general formula of (Zn 1-x Mn x ) SiO 4 .
the phosphor particles may also comprise a green phosphor represented by general formula Ba 1-x Mg x Al 12 O 19 .
the phosphor particles may also comprise a red phosphor represented by general formula Y 1-x Eu x BO 3 .
the phosphor particles may also comprise a red phosphor represented by general formula Y 1-x-y Gd x Eu y BO 3 .
the phosphor particles have preferably spherical or near spherical shape, which enables it to improve the percentage of loading further.
the fourth plasma display panel of the present invention has a plurality of discharge spaces formed between a front panel and a back panel disposed to oppose each other, with a phosphor layer that includes phosphor particles of one of blue, red and green colors being formed in each of the discharge spaces, while the phosphor layers include the second phosphor material powder of the present invention.
the percentage of loading of the phosphor material powder in the phosphor layer can be increased giving the layers good reflective characteristics. This makes it possible to extract the visible light emitted by the phosphor efficiently through the entire surface of the panel, and make a plasma display panel of high luminance and high emission efficiency.
thickness of the phosphor layer is preferably in a range from 5 ⁇ m to 50 ⁇ m inclusive.
the second phosphor material of the present invention is represented by general formula Ba( 1-x-y )Sr y Mg a Al b O c : Eu x , where the value of x is in a range from 0.01 to 0.08 inclusive.
value of x that represents substitution ratio by Eu 2+ ions is generally in a range from 0.1 to 0.15.
the plasma display panel requires another firing process at a temperature around 400°C to bond the front and back panels, that causes deterioration in the emission intensity although this temperature of the second firing is lower than the phosphor firing temperature that is around 500°C.
a phosphor layer of higher emission intensity than that of the phosphor layer of the prior art can be achieved by setting the substitution ratio by Eu 2+ ions as in the configuration of the present invention, thereby increasing the heat resistance. The present invention was completed by finding this fact.
the value of x is preferably in a range from 0.02 to 0.075 inclusive, and more preferably in a range from 0.03 to 0.06 inclusive.
Service life (ultraviolet radiation resistance) of the Ba (1-x) MgAl 10 O 17 : Eu x generally increases as the substitution ratio by Eu 2+ ions is increased. However, the service life and the heat resistance are in the relation of trade-off. Service life of the Ba (1-x) MgAl 10 O 17 :Eu x can be increased by substituting a part of Ba with Sr. Therefore, when the substitution ratio by Eu 2+ ions is decreased as in the second phosphor material of the present invention and substitution ratio by Sr is set as in the present invention at the same time, a phosphor of higher heat resistance and longer service life than the phosphor of the prior art can be obtained.
the value of y is preferably in a range from 0.01 to 0.2 inclusive, more preferably in a range from 0.02 to 0.15 inclusive and further more preferably in a range from 0.02 to 0.1 inclusive.
x + y is preferably in a range from 0.05 to 0.2 inclusive, and more preferably in a range from 0.09 to 0.15 inclusive.
the parameters in the general formula described above may be such as a is 1, b is 10 and c is 17, or alternatively a is 1, b is 14 and c is 23.
the phosphor when applied to the plasma display panel, it is preferable that the phosphor emits visible light when excited by ultraviolet rays and more preferably emits visible light when excited by ultraviolet rays of wavelength 200nm or less.
the fifth plasma display panel of the present invention has a plurality of discharge spaces formed between the front panel and the back panel disposed to oppose each other, with a phosphor layer that includes phosphor particles of one of blue, red and green colors being formed in each of the discharge spaces, while the phosphor layers that contain the blue phosphor particles include the second phosphor material powder of the present invention.
phosphor layers of high heat resistance and high durability can be formed while restraining thermal deterioration during the firing process and suppressing deterioration of the emission intensity when illuminating, thus making it possible to achieve a plasma display panel that has high emission intensity, long service life and high picture quality.
the phosphor layers that contain the blue phosphor particles may be produced through at least one process of firing at a temperature of 400°C or higher.
the phosphor layers that contain the blue phosphor particles may also be produced through at least one process of firing at a temperature of 500°C or higher.
the phosphor layers that contain the blue phosphor particles may also be produced through at least two firing processes.
firing temperature for the phosphor layers that contain the blue phosphor particles is preferably lower in the second firing process than in the first firing process.
the third phosphor material of the present invention is a phosphor material of which base material is partially substituted with Eu 2+ ions, with the substitution ratio by Eu 2+ ions being 8 atomic % or lower.
substitution ratio by Eu 2+ ions is preferably in a range from 1 to 6 atomic %.
the blue phosphor material wherein a certain element in the base material is substituted with Eu 2+ ions that serve as deactivating agent, including a phosphor represented by general formula of BaMgAl y O z , the phosphors of substitution ratio by Eu 2+ ions in a range from 10 to 15 atomic % have been used in the prior art.
luminance and emission intensity can be made higher than in the prior art by forming the phosphor layer using the phosphor material of the present invention.
the invention was completed upon finding that picture quality and luminance of the plasma display panel can be improved by using such phosphor materials as the blue phosphor material.
the third phosphor material of the present invention As described above, it is made possible to form the phosphor layer having heat resistance higher than in the prior art and improve the luminance and emission intensity of the phosphor layer, by setting the Ba substitution ratio by Eu 2+ ions within 8 atomic % or preferably in a range from 1 to 6 atomic % in the phosphor material in which the element to be substituted in the base material is substituted by Eu 2+ ions, particularly a phosphor represented by the general formula of BaMgAl 10 O 17 : Eu 2+ .
the third phosphor material of the present invention preferably contains BaMgAl y O z as the base material with the substitution ratio of Ba by Eu 2+ ions being set within 8 atomic % or preferably in a range from 1 to 6 atomic % also in this case.
values of y and z in the formula BaMgAl y O z of the base material are preferably 10 and 17, respectively.
the values of y and z in the formula BaMgAl y O z of the base material may also be 14 and 23, respectively.
the sixth plasma display panel of the present invention has a plurality of discharge spaces formed between the front panel and the back panel disposed to oppose each other, with a phosphor layer that include phosphor particles of one of blue, red and green colors being formed in each of the discharge spaces, while the blue phosphor particles included in the phosphor layers are made of the third phosphor material powder of the present invention.
the third phosphor material of the present invention is used for the blue phosphor material, as described above, thermal deterioration of the phosphor layer can be suppressed in the firing process during production of the plasma display panel, thus making it possible to improve the picture quality and luminance of the plasma display panel.
a method for forming the phosphor layer according to the present invention is a method of forming the phosphor layer on a substrate, comprising a phosphor material applying step of applying the phosphor material together with a binder, wherein a part of Ba atoms of BaMgAl y O z of the base material are substituted with Eu 2+ ions with the substitution ratio by Eu 2+ ions being within 8 atomic %, and a firing step of firing the substrate whereon the phosphor material is applied.
the phosphor applying step of this forming method may be a process of coating the substrate with an ink or a sheet made by mixing particles of the phosphor material and the binder.
a second method of producing the plasma display panel according to the present invention comprises a phosphor applying step of applying the phosphor material together with the binder onto a first panel substrate, the phosphor material being such as a part of Ba atoms of BaMgAl y O z of the base material are substituted with Eu 2+ ions with the substitution ratio by Eu 2+ ions being in a range from 1 to 6 atomic %, a firing step of firing the first panel substrate whereon the phosphor material has been applied, and a sealing step wherein the first panel and the second panel are placed one on another and sealed following the firing step.
the phosphor applying step of the second producing method may be a process of applying the ink or the sheet made by mixing particles of the phosphor material and the binder onto the first panel substrate.
the sealing step may be a process of placing the first panel and the second panel are placed one on another via a sealing agent then firing and thereby sealing the assembly, following the firing step described above.
Fig. 1A is a schematic sectional view of an AC discharge type plasma display panel (PDP) according to first embodiment of the present invention. While Fig. 1A shows only one cell, the plasma display panel comprises a number of cells that emit red, green and blue light being arranged alternately.
PDP AC discharge type plasma display panel
the plasma display panel comprises a front panel consisting of discharge electrodes 12 and a dielectric glass layer 13 being disposed on a front glass substrate 11, and a back panel consisting of address electrodes 16, barrier ribs 17 and phosphor layers 18 using a flaky phosphor material being disposed on a back glass substrate 15, wherein the front panel and the back panel are laminated with each other to form discharge spaces 19 between the front panel and the back panel that are filled with a discharge gas, while the plasma display panel is driven by applying voltages on the discharge electrodes 12 and the address electrodes 16 by drive circuits shown in Fig. 2.
the discharge electrodes 12 are disposed so as to form an orthogonal matrix with the address electrodes 16.
the front panel 101 is made by forming the discharge electrodes 12 on the front glass substrate 11, forming the lead-or bismuth-based dielectric glass layer 13 to cover thereon, and forming a protective layer 14 on the surface of the dielectric glass layer 13.
the discharge electrodes 12 are electrodes made of silver, and is formed by firing a silver paste that is screen-printed.
the lead-based dielectric glass layer 13 is formed to a thickness of about 20 ⁇ m by firing a coat at 560°C for 20 minutes, the coat being applied by screen printing of, for example, a mixture of 70% by weight of lead oxide [PbO], 15% by weight of boron oxide [B 2 O 3 ] , 10% by weight of silicon oxide [SiO 2 ], 5% by weight of aluminum oxide and an organic binder ( ⁇ -terpineol with 10% of ethyl cellulose dissolved therein).
a coat at 560°C for 20 minutes, the coat being applied by screen printing of, for example, a mixture of 70% by weight of lead oxide [PbO], 15% by weight of boron oxide [B 2 O 3 ] , 10% by weight of silicon oxide [SiO 2 ], 5% by weight of aluminum oxide and an organic binder ( ⁇ -terpineol with 10% of ethyl cellulose dissolved therein).
the protective layer 14 is made of magnesium oxide (MgO) and is formed, for example, to a thickness of about 0.5 to 1.0 ⁇ m by sputtering or CVD (chemical vapor deposition) process.
MgO magnesium oxide
the address electrodes 16 are formed on the back glass substrate 15 by screen printing process similarly to the discharge electrodes 12.
the barrier ribs 17 may be formed by screen printing or the like, but may also be formed by spraying process as described below.
Fig. 3A through Fig. 3F show the method of forming the barrier ribs by the spraying process.
a dry film 81 made of an acrylic photosensitive resin Fig. 3B.
the dry film 81 is patterned by photolithography process. Specifically, the dry film 81 covered by a photo mask 82 is irradiated with ultraviolet (UV) rays 83 only on portions where the barrier ribs are to be formed (Fig. 3C), and developed. Thus the dry film 81 is removed from the portions where the barrier ribs are to be formed so that a mask of the dry film 81 is formed only on the portions where the barrier ribs are not to be formed (Fig. 3D) . Development is carried out in an aqueous solution of alkali (specifically, aqueous solution of sodium carbonate) with about 1% of concentration.
alkali specifically, aqueous solution of sodium carbonate
the dry film is then subjected to plasma spraying of alumina (Al 2 O 3 ) ,spinel (MgO ⁇ Al 2 O 3 ) and zircon (ZrO 3 ) that are the raw materials to make the barrier ribs.
alumina Al 2 O 3
spinel MgO ⁇ Al 2 O 3
zircon ZrO 3
an oxide such as Cr 2 O 3 , TiO 2 , CoO, Fe 2 O 3 or MnO 2 or a mixture thereof that have black color, too, may also be sprayed onto alumina, spinel and zircon.
Fig. 4 shows the plasma spray coating process.
the plasma spray apparatus 90 generates a plasma jet by applying a voltage across a cathode 91 and an anode 92 thereby generating an arc discharge from the tip of the cathode 91 while supplying argon gas thereto.
powder of raw materials (alumina, Cr 2 O 3 , TiO 2 , etc.) is supplied into the plasma jet so that the materials are melted in the plasma jet and sprayed onto the surface of the substrate 15.
the substrate 15 with the film 84 formed thereon (Fig. 3E) is immersed in a solution of removing agent (sodium hydroxide solution) to remove the mask of the dry film 81 (lift-off process) .
removing agent sodium hydroxide solution
the process of forming the phosphor layer 18, to be described in detail later, consists of the application of a phosphor ink by continuously spouting the phosphor ink from a nozzle and firing thereof.
the barrier ribs are formed to a height of 0.1 to 0.15 mm at intervals of 0.15 to 0.3 mm.
the front panel 101 and the back panel 102 produced as described above are put together by using sealing glass, while evacuating the inside of the discharge spaces 19 separated by the barrier ribs 17 to a high level of vacuum (for example, 8 ⁇ 10 -7 Torr), then filling the discharge spaces with a discharge gas (for example, He-Xe or Ne-Xe inert gas) at a predetermined pressure, thereby producing the plasma display panel.
a discharge gas for example, He-Xe or Ne-Xe inert gas
a circuit block (panel drive circuits 151, 152, 153) that drive the plasma display panel are mounted as shown in Fig. 2, thereby producing the display apparatus of the plasma display panel.
the discharge gas includes 5% by volume of Xe and the sealing pressure is set in a range from 500 to 800 Torr.
Fig. 5 schematically shows the constitution of an ink application device 20 used when forming the phosphor layer 18.
the ink application device 20 has a server 21 that stores the phosphor ink and a pressurizing pump 22 that pressurizes the ink and supplies it to a header 23.
the header 23 is provided with an ink chamber 23a and a nozzle 24, so that the ink that has been pressurized and supplied to the ink chamber 23a is continuously spouted from the nozzle 24.
the header 23 is formed integrally with the ink chamber 23a and the nozzle 24 by mechanical machining and electric discharge machining of a metallic material.
the phosphor ink is made by mixing the phosphor particles of different colors, the binder and the solvent with a surfactant, silica and other components to obtain an appropriate level of viscosity.
phosphor particles that constitute the phosphor ink those commonly used in the phosphor layers of plasma display panels can be used. Specific examples are as follows:
average particle size of the flaky phosphor particles used in the phosphor ink is preferably within 6 ⁇ m.
profile ratio (breadth/thickness) of the phosphor particles is preferably in a range from 3 to 25.
Viscosity of the phosphor ink is preferably controlled to be within 1000 centipoise (from 15 to 1000 centipoise) at 25°C.
Particle size of silica used as an additive is preferably in a range from 0.01 to 0.02 ⁇ m, with the content thereof being preferably from 1 to 10% by weight, and 0.1 to 5% by weight of a dispersing agent is preferably added.
the inner diameter of the nozzle 24 no smaller than 45 ⁇ m to prevent clogging of the nozzle and smaller than the groove width W between the barrier ribs 17, normally in a range from 45 to 150 ⁇ m.
the ink is stored while being mixed and agitated by an agitator (not shown) installed in the server 21.
Discharge pressure of the pressurizing pump 22 is controlled so that the ink discharged from the nozzle 24 forms a continuous stream.
the header 23 is adapted to scan over the back glass substrate 15, while scanning of the header 23 is effected by a header scanning mechanism (not shown) that drives the header 23 linearly in the first embodiment.
the glass substrate may also be linearly driven while fixing the header 23.
the ink application device 20 may also be made in such a configuration as shown in Fig. 6, where the header 23 has a plurality of nozzles 24 so that the ink is discharged from the nozzles 24 in parallel while scanning (scanning direction is indicated by an arrow A in Fig. 6). Providing the plurality of nozzles 24 makes it possible to formed a plurality of ink lines 25 in a single operation.
the phosphor ink by the ink application device 20 is carried out along the barrier ribs 17 on the back glass substrate 15 for each of the red, blue and green colors. After drying the red, blue and green phosphor inks that have been applied successively in the respective grooves, the panel is fired (at around 500°C for 10 minutes) thereby forming the phosphor layers 18.
the phosphor layers 18 are formed by applying the ink continuously, not by applying ink droplets as in the conventional ink jet process, and therefore the layers can be formed with a uniform thickness.
each header 23 has three ink chambers and nozzles for the individual colors of red, blue and green, so that phosphor inks of three colors are discharged in parallel, it is made possible to apply the phosphor inks of the three colors in a single scanning operation.
the phosphor particles used in the first embodiment consist of metal oxides that have been used in the prior art.
Specific compositions of the phosphor particles of different colors are: BaMgAl 10 O 17 : Eu 2+ based on the crystal skeleton of BaMgAl 10 O 17 with a predetermined amount of europium Eu included as an activation agent for the blue phosphor particles, YBO 3 : Eu 3+ based on the crystal skeleton of YBO 3 with a predetermined amount of Eu included as an activation agent for the red phosphor particles and Zn 2 SiO 4 : Mn 2+ based on the crystal skeleton of Zn 2 SiO 4 with a predetermined amount of Mn included as an activation agent for the green phosphor particles.
phosphor particles that have greater values of profile ratio (breadth/thickness) (flat and thinner) than the conventional ones for these phosphor particles.
the use of the phosphor particles having larger profile ratio makes it possible to increase the coverage ratio by the phosphor particles in the phosphor layer 18 of each cell, efficiency of absorbing the ultraviolet rays generated by electric discharge can be increased, thereby increasing the luminance of the panel.
phosphor particles 181 having spherical shape are sued as shown in Fig. 1C, for example, since overlapping ratio (coverage ratio) between the phosphor particles 181 becomes relatively small in the incident direction (indicated by an arrow schematically in the drawing) of the ultraviolet ray, larger portion- of the ultraviolet rays is absorbed by the phosphor particles 181 at relatively deeper positions from the surface.
Light emitted from the phosphor particles 18a that have absorbed the ultraviolet rays at positions relatively nearer to the surface of the phosphor layer 18 is less likely to be absorbed by other phosphor particles 18a and is emitted from the surface, and therefore effectively contribute to the improvement in the luminance of the panel As a result, the emission efficiency of the phosphor layer 18 can be increased in the first embodiment.
Such flaky phosphor particles as described above can be made by firing at a relatively higher temperature for a shorter period of time than in the prior art, thereby suppressing the growth of crystal in the direction of thickness of the phosphor particles.
the red phosphor such as YBO 3 and YGdBO 3 may also be formed in flaky phosphor particles by using a hydroxide such as Y 2 (OH) 3 as a starting material or employing hydrothermal synthesis (high temperature, high pressure synthesis) process.
a hydroxide such as Y 2 (OH) 3
hydrothermal synthesis high temperature, high pressure synthesis
Ranges of average flake diameters and average flake thickness are limited for the following reasons.
the average flake diameter is less than 0.3 ⁇ m or the average flake thickness is 0.1 ⁇ m or less, the phosphor particles that are too fine tend to coagulate, resulting in a decrease in the absorption efficiency.
the average flake diameter is 0.3 ⁇ m or less and the average flake thickness is 0.1 ⁇ m or less, much of the phosphor particles cannot be formed in the desired crystal structure, thus making it likely that the phosphor cannot provide enough luminance.
coagulation of the phosphor particles can be restrained to some extent by selecting a proper combination of the solvent wherein the phosphor particles are dispersed and other agents used when forming the phosphor layer. And in this case, phosphor particles of even smaller diameters and larger profile ratio (breadth/thickness) can be used.
the blue phosphor particles are made by, first, mixing raw materials of barium carbonate (BaCO 3 ), magnesium carbonate (MgCO 3 ) and aluminum oxide ( ⁇ -Al 2 O 3 ) in a proportion of 1: 1: 10 by the numbers of atoms of Ba, Mg and Al. Then a predetermined amount of europium oxide (Eu 2 O 3 ) is added to the mixture. Then the mixture is mixed with a proper amount of a flux (AlF 2 , BaCl 2 ) in a ball mill and the mixture is fired in a weakly reducing atmosphere (H 2 , N 2 ) at a temperature in a range from 1400 to 1650°C for a predetermined period of time (for example, 0.5 hours). Flaky crystal is obtained by sieving the fired mixture.
BaCO 3 barium carbonate
MgCO 3 magnesium carbonate
⁇ -Al 2 O 3 aluminum oxide
Eu 2 O 3 europium oxide
Flaky crystal is obtained by sieving the fired mixture.
the profile ratio (breadth/thickness) can be changed by changing the firing temperature, ratio of the H 2 and N 2 flow rates and firing time.
the red phosphor particles are made by mixing raw materials of yttrium hydroxide Y 2 (OH) 3 and boric acid (H 3 BO 3 ) in a proportion of 1: 1 by the numbers of atoms of Y and B. Then a predetermined amount of europium oxide (Eu 2 O 3 ) is added to the mixture, which is mixed with a proper amount of flux in a ball mill. After firing the mixture at a temperature in a range from 1200 to 1450°C in air for a predetermined period of time (for example, one hour), flaky powder is obtained by sieving the fired mixture.
a predetermined amount of europium oxide Eu 2 O 3
the green phosphor particles are made by mixing raw materials of zinc oxide (ZnO) and silicon oxide (SiO 2 ) in a proportion of 2: 1 by the numbers of atoms of Zn and Si. Then a predetermined amount of manganese oxide (Mn 2 O 3 ) is added to the mixture, which is mixed in a ball mill. After firing the mixture at a temperature in a range from 1200 to 1350°C in air for a predetermined period of time (for example, 0.5 hours), flaky powder is obtained by sieving the fired mixture.
ZnO zinc oxide
SiO 2 silicon oxide
Mn 2 O 3 manganese oxide
the flake diameters and the flake thickness can be determined by observing the powder under an electron microscope, and the values given in this specification have been obtained with an electron microscope.
the red phosphor particles that have cubic crystal system, have a profile ratio that is a little smaller than those of the blue and green phosphor particles which have hexagonal plate shape. Thus it is necessary to make the flake diameter of the red phosphor particles a little smaller.
the profile ratio can be controlled by changing the firing temperature and the firing time.
phosphor particles of large profile ratio may also be used for only one color or two colors.
such a constitution may be employed as phosphor particles of large profile ratio are used for only blue phosphor particles and conventional spherical particles are used for the red and green phosphor particles. With this constitution, luminance of the display panel can be improved.
the phosphor layer 18 of the first embodiment is formed by the ink jet process. Since an ink of relatively low viscosity is used in this process, spherical phosphor particles having large diameters used in the prior art tend to precipitate thereby making it difficult to coat the side face of a barrier rib with phosphor layer with the phosphor particles being uniformly dispersed therein.
the phosphor particles used in the first embodiment that have small diameters and large profile ratio, on the other hand, are less likely to precipitate in the ink and therefore makes it possible to coat the side face of a barrier rib with phosphor layer having the phosphor particles being uniformly dispersed. Thus it is made possible to increase the coverage ratio by the phosphor particles in the phosphor layer and increase the luminance at the same time.
the use of the laminar phosphor particles and the low-viscosity ink makes it possible to completely cover the side faces of the barrier ribs and the bottom surface with the phosphor without generating gaps between the phosphor particles in the incident direction of the ultraviolet rays (Fig. 1B) even when the phosphor layer is thick due to many flaky particles being stacked one on another in the drying process after pouring the phosphor ink in to the space between the barrier ribs.
total weight of the phosphor can be reduced, contributing to the cost reduction of the panel.
samples Nos.1 through 7 are samples of the examples according to the present invention, and samples Nos.8 through 10 are Comparative Examples.
Tables 1, 2 and 3 show the conditions of making the blue, red and green phosphors.
the plasma display panels of the sample Nos. 1 through 7 are plasma display panels produced according to the first embodiment described above, with phosphor particles that are different in flake diameter, thickness, profile ratio (breadth/thickness) and particle diameter by changing the firing temperature, firing time and gas flow rate, with various values being set for the concentration of activation agent to be added.
the plasma display panels of sample Nos. 1 through 7 are produced with the phosphor particles thereof being fired at progressively higher temperatures with the average flake diameter progressively increasing in this order. Average flake thickness is set to be smaller by setting the firing time shorter. Concentration of the activation agent did not had significant effect on the luminance within the range of concentrations for each color.
Plasma display panels of Examples and Comparative Examples were set as 20 ⁇ m for thickness of the dielectric glass layer, 0.5 ⁇ m for thickness of the MgO protective layer and 0.08 mm for distance between discharge electrodes.
the plasma display panels of sample Nos. 8 through 10 are produced with similar settings as those of the plasma display panels of the sample No. 7, except for controlling the firing temperature and the firing time of the blue phosphor particles to obtain smaller profile ratio.
viscosity of the ink was controlled by combining the resin, solvent, dispersion agent or the like according to the particle size and profile ratio to make it possible to continuously spout the phosphor ink from the nozzles, and such a phosphor layer was obtained that had satisfactory shape of applied coat (capable of forming the phosphor layer also on the side surface of the barrier rib) with the viscosity of ink being in a range from 15 to 1000 centipoise.
barrier ribs In the process of forming the barrier ribs by the spray process, while a high luminance can be obtained by using only white alumina (Al 2 O 3 ) , zircon (ZrO 2 ) and spinel (MgO ⁇ Al 2 O 3 ), display contrast of the panel can be improved by providing a black barrier rib material such as chromium oxide (Cr 2 O 3 ), Al 2 O 3 -TiO 2 , CoO, MnO 2 and Fe 2 O 3 on top of the barrier ribs (samples Nos.1 through 9).
Luminance was measured on the plasma display panels of samples Nos. 1 through 10, under electric discharge conditions of 150V for discharge holding voltage and 30kHz for frequency. Results of the measurements are shown in Table 6.
Luminance was measured on each plasma display panel while illuminating in white color over the entire surface, as the emission layer of every color is set to achieve white balance while emitting light.
Ratio of luminance when the panel was illuminated to luminance when the panel was turned off was determined in a dark room to determine the display contrast.
Comparison of the results of measurements on the plasma display panels of samples Nos. 1 through 7 and the plasma display panels of samples Nos. 8 through 10 shows that greater improvement in luminance can be achieved when flake diameters of the blue phosphor particles are in a range from 0.3 to 6 ⁇ m, the flake thickness is in a range from 0.1 to 2 ⁇ m and profile ratio is in a range from 3 to 25.
Fig. 9 is a schematic sectional view of an AC discharge type plasma display panel (PDP) according to the second embodiment of the present invention. While Fig. 9 shows only one cell, the plasma display panel comprises a number of cells that emit red, green and blue light being arranged thereon.
PDP AC discharge type plasma display panel
the plasma display panel of the second embodiment comprises the front panel 101 consisting of the display electrodes 12, the dielectric glass layer 13 and the protective layer 14 being disposed on the front glass substrate (front cover plate) 11, and a back panel 201 consisting of the address electrodes 16, a visible light reflecting layer 217, barrier ribs 218 and phosphor layers 219 disposed on the back glass substrate (back plate) 15, wherein the front panel 101 and the back panel 201 are laminated with each other to form the discharge spaces between the front panel 101 and the back panel 201 that are filled with a discharge gas. Producing process will be described in detail below.
the front panel 101 is formed similarly to the first embodiment.
a silver electrode paste is screen-printed on the back glass substrate 15 and is then fired to form the address electrodes 16, over which the visible light reflecting layer 217 comprising TiO 2 particles and dielectric glass is formed by screen printing and firing, and the barrier ribs 218 made of glass are formed at predetermined intervals by repeating screen printing and then firing.
the phosphor layer 219 that includes one from among red phosphor particles, green phosphor particles and blue phosphor particles is formed in each of the spaces (that become discharge spaces when put together with the front panel 101) separated by the barrier ribs 218.
the phosphor layer 219 is formed by continuously spouting the phosphor ink from the nozzles while scanning, and then firing at a temperature of around 500°C in air, similarly to the first embodiment.
the phosphor layer 219 may also be formed by applying the phosphor ink by screen printing process, or by making a sheet wherein the phosphor particles are dispersed and laminating the sheet.
the plasma display panel of the second embodiment was produced according to the specifications of a 40-inch class high definition television set, with the barrier ribs formed to a height of 0.1 to 0.15 mm at intervals of 0.15 to 0.3 mm, while the phosphor layers 219 are formed on the back cover surface and on side surfaces of the barrier ribs to thickness of 5 to 50 ⁇ m including phosphor particles of average particle size in a range from 0.5 to 3 ⁇ m.
the front panel 101 and the back panel 201 made as described above are put together by using sealing glass so that the display electrodes 12 of the front panel 101 and the address electrodes 16 cross at right angles with each other, then after being fired at a temperature around 450°C, the inside of the discharge spaces separated by the barrier ribs 218 was evacuated to a high level of vacuum (8 ⁇ 10 -7 Torr), followed by filling of the discharge spaces with a discharge gas of predetermined composition at a predetermined pressure, thereby fabricating the plasma display panel.
the neon (Ne)-xenon (Xe) discharge gas was prepared to include 5% by volume of Xe and the sealing pressure was set in a range from 500 to 800 Torr.
the second embodiment employs the following materials for the phosphor materials that constitute the phosphor ink.
Green phosphor material Zn 2 SiO 4 : Mn 2+
Red phosphor material Y 2 O 3 : Eu 3+
(Y x Gd 1-x )BO 3 Eu 3+
Fig. 8A and Fig. 8B show the relative luminance and relative emission intensity of the following blue phosphor materials before and after the firing process with the value of x being changed.
Ba (1-x) Eu x MgAl 10 O 17 Ba 2(1-x) Eu 2x Mg 2 Al 12 O 22
Solid lines in Fig. 8A, 8B show the characteristic of the blue phosphor materials before firing
dashed lines show the characteristic of the blue phosphor materials after firing at 520°C in air
alternate dot and dash lines show the characteristic after firing at 460°C in air following the firing at 520°C.
the results described above show that the amount of Eu ions that can substitute Ba ions in the layer that contains Ba is in a range from 1 atomic % to 10 atomic %.
the phosphor materials of different colors used in the second embodiment can be made as follows. Blue phosphor materials of Ba (1-x) Eu x MgAl 10 O 17 , Ba 2(1- x) EU 2x Mg 2 Al 12 O 22 , Ba 2(1-x) Eu 2x Mg 4 Al 8 O 18 and Ba 3(1-x) Eu 3x Mg 5 Al 18 O 35 are made by mixing barium carbonate (BaCO 3 ), magnesium carbonate (MgCO 3 ), aluminum oxide ( ⁇ -Al 2 O 3 ) and europium oxide (EU 2 O 3 ) in predetermined proportion of the number of atoms.
the mixture is mixed with a proper amount of flux (AlF 2 , BaCl 2 ) in a ball mill and the mixture is fired in a reducing atmosphere (H 2 , N 2 ) at a temperature in a range from 1400 to 1650°C for a predetermined period of time (for example, 0.5 hours).
a proper amount of flux AlF 2 , BaCl 2
a reducing atmosphere H 2 , N 2
the red phosphor material is made by mixing the raw materials of yttrium hydroxide Y 2 (OH) 3 and europium oxide (Eu 2 O 3 ) which is mixed with a proper amount of flux in a ball mill, then the mixture is fired at a temperature in a range from 1200 to 1450°C in air for a predetermined period of time (for example, one hour) .
the green phosphor material is made by mixing the raw materials of zinc oxide (ZnO) and silicon oxide (SiO 2 ) in a proportion of 2: 1 by the numbers of atoms of Zn and Si. Then a predetermined amount of manganese oxide (Mn 2 O 3 ) is added to the mixture, which is mixed in a ball mill, and then fired at a temperature in a range from 1200 to 1350°C in air for a predetermined period of time (for example, 0.5 hours).
ZnO zinc oxide
SiO 2 silicon oxide
Mn 2 O 3 manganese oxide
the plasma display panels (PDP) of samples No. 201, 203, 204, 206 through 208, 210 through 212, 214 through 216 and 218 through 220 are plasma display panels of Example 2 produced according to the second embodiment, while changing the value of x in the blue phosphor materials (Ba (1-x) Eu x MgAl 10 O 17 , Ba 2(1- x) Eu 2x Mg 2 Al 12 O 22 Ba 2(1-x) Eu 2x Mg 4 Al 8 O 19 Ba 3(1-x) Eu 3x Mg 5 Al 18 O 35 ) .
the samples Nos. 202, 205, 209, 213 and 217 are plasma display panels of Comparative Examples.
the color temperature non-adjusted luminance given in Table 7 refers to the luminance of white display with the same signals given for all colors, and color temperature-adjusted luminance refers to the luminance when the signals of different colors are adjusted to achieve color temperature of 9500 degrees in white display.
Fig. 11 is a schematic sectional view showing the AC discharge type plasma display panel of the third embodiment of the present invention.
the plasma display panel of the third embodiment has a constitution similar to that of the second embodiment, except that the phosphor layers 219 of the second embodiment is replaced by phosphor layers 319 that include phosphor particles and non-fluorescent white particles of smaller particle size than the phosphor particles in a predetermined proportion.
the plasma display panel of the third embodiment since the phosphor layers 319 that include the phosphor particles and the non-fluorescent white particles of smaller particle size than the phosphor particles in the predetermined proportion is used, has various excellent features to be described later.
the phosphor layers 319 are formed by continuously spouting the phosphor ink from the nozzles while scanning thereby applying the phosphor ink and firing the ink, similarly to the second embodiment. While Fig. 3 shows only one cell, the plasma display panel comprises a number of cells that emit red, green and blue light being arranged thereon.
the phosphor particles contained in the phosphor layers 319 may be those commonly used in the phosphor layers of the plasma display panel of the prior art. Specifically, the following materials may be used. Blue phosphor particles: BaMgAl 10 O 17 : Eu 2+ Green phosphor particles: Zn 2 SiO 4 : Mn 2+ or BaMgAl 12 O 19 : Mn 2+ Red phosphor particles: YBO 3 : Eu 3+ , (Y x Gd 1-x )BO 3 : Eu 3+
Fig. 12 schematically shows the particle size distribution of the conventional phosphor material
Fig. 10 schematically shows the particle size distribution of the phosphor material of the third embodiment.
distribution 1a of the non-fluorescent white particles is shown on the left and distribution 1b of the phosphor particles is shown on the right.
Percentage of loading of the phosphor particles in the phosphor layer generally increases as the particle sizes of the phosphor particles are decreased, leading to higher reflecting effect inside the layer when the percentage of loading is higher, thus making it possible to extract the emitted visible light effectively through the front surface of the layer.
the average particle size of the phosphor particles 1.5 ⁇ m or larger for suppressing deterioration due to crystal defects from appearing significantly, while it is effective to keep the average particle size within 5 ⁇ m for achieving a sufficient level of percentage of loading in the layer. It is also made possible to efficiently fill the voids between the phosphor particles by setting the average particle size of the non-fluorescent white particles to 1.5 ⁇ m or smaller. While the percentage of loading begins to increase when the average particle size of the non-fluorescent white particles decreases below a half that of the phosphor particles, this effect becomes remarkable when the average particle size of the non-fluorescent white particles is 1/5 that of the phosphor particles or smaller.
the phosphor layer of the plasma display panel generally employs the phosphor particles individually, in such a case it is effective in increasing the emission efficiency to use the flaky phosphor particles as shown in the first and the second embodiments.
the phosphor particles and the non-fluorescent white particles are used together as in the third embodiment, remarkable effect of increasing the percentage of loading can be achieved by making the particles in spherical or near spherical shape.
the reflectivity approaches a plateau when the thickness reaches 50 ⁇ m or more, and the luminance decreased due to low coverage ratio when the thickness was less than 5 ⁇ m. Therefore thickness of the phosphor layer 319 is preferably in a range from 5 ⁇ m to 50 ⁇ m inclusive.
the phosphor particles of different colors used in the third embodiment are made as described below.
the blue phosphor particles are made by, first, mixing the raw materials of barium carbonate (BaCO 3 ), magnesium carbonate (MgCO 3 ) and aluminum oxide ( ⁇ -Al 2 O 3 ) in a proportion of 1: 1: 10 by the numbers of atoms of Ba, Mg and Al.
Eu 2 O 3 europium oxide
the mixture is mixed with a proper amount of flux (AlF 2 , BaCl 2 ) in a ball mill and the mixture is fired in a weakly reducing atmosphere (H 2 , N 2 ) at a temperature in a range from 1400 to 1650°C for a predetermined period of time (for example, 0.5 hours), before being sieved.
a proper amount of flux AlF 2 , BaCl 2
H 2 , N 2 a weakly reducing atmosphere
the red phosphor particles are made by mixing the raw materials of yttrium hydroxide Y 2 (OH) 3 and boric acid (H 3 BO 3 ) in a proportion of 1: 1 by the numbers of atoms of Y and B.
Eu 2 O 3 europium oxide
the green phosphor particles are made by mixing the raw materials of zinc oxide (ZnO) and silicon oxide (SiO 2 ) in a proportion of 2: 1 by the numbers of atoms of Zn and Si. Then a predetermined amount of manganese oxide (Mn 2 O 3 ) is added to the mixture, which is then mixed in a ball mill. After firing the mixture at a temperature in a range from 1200 to 1350°C in air for a predetermined period of time (for example, 0.5 hours) , the fired mixture is sieved.
ZnO zinc oxide
SiO 2 silicon oxide
Mn 2 O 3 manganese oxide
the desired mixed phosphor material powder is obtained by mixing the phosphor particles of different colors, that have the predetermined average particle size that have been sieved in the processes described above, with the non-fluorescent white particles.
the coefficient of particle size concentration can also be controlled in the above process.
Spherical or near spherical phosphor particles can be made by using spherical ⁇ -Al 2 O 3 particles as the material for the blue phosphor particles and spherical SiO 2 particles as the material for the green phosphor particles.
Spherical blue phosphor particles can also be made by the process described in, for example, Unexamined Patent Publication (Kokai) Nos. 62-201989 and 7-268319.
the plasma display panels of samples Nos. 301 through 308 shown in Table 8 are the plasma display panel of this example of the present invention produced according to the third embodiment described above, while changing the particle size, coefficient of particle size concentration or particle shape.
the particle size distribution is determined by the coal tar counter method wherein the number of particles falling in an interval of 0.1 ⁇ m is converted to the proportion to the total number of particles.
the plasma display panels of samples Nos. 309 through 313 are the plasma display panels of Comparative Examples.
Spherical TiO 2 particles were used as the non-fluorescent white particles, with the proportion of the number of phosphor particles to the number of TiO 2 particles set to 2: 1 for every color.
thickness of the phosphor layer was set to 20 ⁇ m and discharge gas pressure was set to 500 Torr.
Luminance of the plasma display panels was measured under electric discharge conditions of 150V for discharge holding voltage and 30kHz for frequency.
Luminance was measured on each plasma display panel while illuminating in white color over the entire surface, as the phosphor layer of every color is set to achieve white balance while emitting light.
the luminance can be increased by mixing the non-fluorescent white particles having particle sizes smaller than the phosphor particles.
Fig. 14 is a schematic sectional view of an AC discharge type plasma display panel according to the fourth embodiment of the present invention. While Fig. 14 shows only one cell, the plasma display panel comprises a number of cells that emit red, green and blue light being arranged thereon.
the plasma display panel of the fourth embodiment has a constitution similar to that of the second embodiment, except that the phosphor layers 219 of the second embodiment are replaced by phosphor layers 419 that includes phosphor material powder comprising phosphor particles having predetermined particle size distribution.
the plasma display panel of the fourth embodiment being constituted by using the phosphor layers 419, has various excellent features to be described later.
the phosphor layers 419 are formed by continuously spouting the phosphor ink from the nozzles while scanning thereby applying the phosphor ink and firing the ink, similarly to the second embodiment.
the phosphor material commonly used in the phosphor layer of the plasma display panel may be used. Specifically, the following materials may be used. Blue phosphor material: BaMgAl 10 O 17 : Eu 2+ Green phosphor material: Zn 2 SiO 4 : Mn 2+ or BaAl 12 O 19 : Mn 2+ Red phosphor material: YBO 3 : Eu 3+ , (Y x Gd 1-x )BO 3 : Eu 3+
Fig. 15 schematically shows the particle size distribution of the conventional phosphor material powder
Fig. 13 schematically shows the particle size distribution of the phosphor material powder of the fourth embodiment.
the phosphor material powder of the fourth embodiment is made such as the proportion of relatively small phosphor particles is increased and the proportion of relatively large phosphor particles is decreased, so that voids between the large phosphor particles are filled with the small phosphor particles to increase the percentage of loading, resulting in higher reflecting effect inside the layer, thus making it possible to extract the emitted visible light effectively through the front surface of the layer.
the percentage of loading can be increased by setting the number of phosphor particles greater than Dp to 70% or less of the number of phosphor particles smaller than Dp, and the percentage of loading is increased further by setting the proportion to 50% or lower.
the average particle size it is preferable to set the average particle size to 1.5 ⁇ m or larger for suppressing deterioration due to crystal defects from appearing significantly, while it is preferable to set the average particle size to 5 ⁇ m or smaller for achieving a sufficient level of coverage in the phosphor layer.
the thickness was less than 5 ⁇ m on the other hand, the luminance decreased due to low coverage ratio.
the phosphor materials of different colors used in the fourth embodiment are made as described below.
the blue phosphor particles are made by, first, mixing the raw materials of barium carbonate (BaCO 3 ), magnesium carbonate (MgCO 3 ) and aluminum oxide ( ⁇ -Al 2 O 3 ) in a proportion of 1: 1: 10 by the numbers of atoms of Ba, Mg and Al.
Eu 2 O 3 europium oxide
the mixture is mixed with a proper amount of flux (AlF 2 , BaCl 2 ) in a ball mill and the mixture is fired in a weakly reducing atmosphere (H 2 , N 2 ) at a temperature in a range from 1400 to 1650°C for a predetermined period of time (for example, 0.5 hours).
the red phosphor particles are made by mixing the raw materials of yttrium hydroxide Y 2 (OH) 3 and boric acid (H 3 BO 3 ) in a proportion of 1: 1 by the numbers of atoms of Y and B. Then a predetermined amount of europium oxide (Eu 2 O 3 ) is added to the mixture, which is mixed with a proper amount of flux in a ball mill and fired at a temperature in a range from 1200 to 1450°C in air for a predetermined period of time (for example, one hour) .
Eu 2 O 3 europium oxide
the green phosphor particles are made by mixing the raw materials of zinc oxide (ZnO) and silicon oxide (SiO 2 ) in a proportion of 2: 1 by the numbers of atoms of Zn and Si. Then a predetermined amount of manganese oxide (Mn 2 O 3 ) is added to the mixture and then mixed in a ball mill. The mixture is fired at a temperature in a range from 1200 to 1350°C in air for a predetermined period of time (for example, 0.5 hours).
the phosphor material powder having the desired particle size distribution is obtained by sieving the phosphor particles made in the processes described above.
Spherical or near spherical phosphor particles of the blue phosphor and the green phosphor can be made by making ⁇ -Al 2 O 3 particles used as the material for the blue phosphor particles and SiO 2 particles used as the material for the green phosphor particles in spherical shape.
Spherical blue phosphor particles can also be made by the process described in, for example, Unexamined Patent Publication (Kokai) Nos. 62-201989 and 7-268319.
the plasma display panels of samples Nos. 401 through 406 are the plasma display panels of this example produced according to the fourth embodiment described above, while changing the peak particle size Dp, minimum particle size Dmin, maximum particle size Dmax, particle size distribution and phosphor particles shape.
the particle size distribution shown in Table 9 is determined by the coal tar counter method wherein the number of particles falling in an interval of 0.1 ⁇ m is converted to the proportion to the total number of particles.
the plasma display panels of samples Nos. 407 through 410 are plasma display panels of Comparative Examples.
thickness of the phosphor layer was set to 20 ⁇ m and discharge gas pressure was set to 500 Torr.
Luminance of the plasma display panels was measured under electric discharge conditions of 150V for discharge holding voltage and 30kHz for frequency.
Luminance was measured on each plasma display panel while illuminating in white color over the entire surface, as the phosphor layer of every color is set to achieve white balance while emitting light.
the luminance can be increased by setting the number of phosphor particles that are greater than Dp less than the number of phosphor particles that are smaller than Dp, or setting the value of Dmax - Dp less than the value of Dp - Dmin. This may be because, in the constitution of this example, voids between the phosphor particles of relatively large particle sizes are filled densely with the phosphor particles of smaller particle sizes, resulting in higher reflectivity of the phosphor layer.
Comparison of samples No. 403 and No. 404 shows that the luminance can be increased more remarkably by decreasing the proportion of the number of phosphor particles greater than Dp to the number of phosphor particles smaller than Dp from within 70% to 50%.
Comparison of samples No. 402 and No. 403 also shows that improvement in the luminance becomes remarkable by setting the value of Dmax - Dp less than 0.5 times the value of Dp - Dmin, and further higher by setting the former less than 0.3'times the latter.
sample No. 401 improvement in the luminance was small because the peak particle size was relatively large and sufficient coverage ratio could not be obtained with a film of 20 ⁇ m in thickness.
sample No. 406 because the peak particle size was relatively small, the phosphor included much crystal defects and therefore resulted in small improvement in luminance.
the plasma display panel of the fifth embodiment of the present invention will be described below.
Fig. 20 is a schematic sectional view of an AC discharge type plasma display panel according to the fifth embodiment. While Fig. 20 shows only one cell, the plasma display panel comprises a number of cells that emit red, green and blue light being arranged thereon.
the plasma display panel of the fifth embodiment has a constitution similar to that of the second embodiment, except that the phosphor layers 219 of the second embodiment are replaced by phosphor layers 519 that include a phosphor material having predetermined composition.
the plasma display panel of the fifth embodiment being constituted by using the phosphor layers 519 that include the phosphor material of the predetermined composition which will be described in detail later has various excellent features to be described later.
the phosphor layers 519 are formed by continuously spouting the phosphor ink from the nozzles while scanning thereby applying the phosphor ink and firing the ink, similarly to the second embodiment.
Fig. 20 shows only one cell, the plasma display panel comprises a number of cells that emit red, green and blue light being arranged thereon.
the phosphor material commonly used in the phosphor layer of the plasma display panel of the prior art may be used except for the blue phosphor. Specifically, the following materials may be used. Green phosphor material: Zn 2 SiO 4 : Mn or BaAl 12 O 19 : Mn Red phosphor material: YBO 3 : Eu or (Y x Gd 1-x )BO 3 : Eu
Composition of Ba (1-x-y) Sr y Mg a Al b O c : Eu x was used for the blue phosphor.
Fig. 16A and Fig. 16B show the relative emission intensity of the phosphor materials of Ba 0.95-x Sr 0.05 MgAl 10 O 17 : Eu x and Ba 1-x MgAl 10 O 17 : Eu x before and after the firing process when the value of x changed. Relative emission intensity is given relative to the emission intensity of Ba 0.9 MgAl 10 O 17 :Eu 0.1 before firing that is assumed to be 100.
Solid lines in Fig. 16A, 16B show the characteristics of the phosphor materials of different colors before firing
dashed lines show the characteristics of the phosphor materials after firing at 520°C in air
alternate dot and dash lines show the characteristics of the phosphor materials after firing at 460°C in air following the firing at 520°C.
Ba 0.95-x Sr 0.05 MgAl 10 O 17 :Eu x and Ba 1-x MgAl 10 O 17 : Eu x show similar properties, in a comparison of the emission intensity, composition without Sr showed about 1 to 2% higher emission intensity.
the phosphor material that is activated by Eu 2+ ions and has the composition in the form of Ba (1-x-y) Sr y Mg a Al b O c : Eu x is not limited to Ba (1-x-y) Sr y MgAl 10 O 17 : Eu x , and similar effect was obtained also by using Ba (1-x-y) Sr y MgAl 14 O 23 : Eu x and the like.
the blue phosphor material used'in the plasma display panel of the fifth embodiment has a problem in service life, and it is necessary to study the durability of the phosphor material to be used.
Fig. 17 shows the durability of the phosphor material Ba 1-x MgAl 10 O 17 : Eu x when the value of x is changed. Emission intensity after illuminating for 5000 hours relative to the emission intensity in the early stage of panel illumination that is assumed to be 100 is plotted along ordinate and the value of x is plotted along abscissa.
Fig. 18 shows the durability of the phosphor material having composition of Ba 0.95-y) Sr y MgAl 10 O 17 : Eu 0.05 with different values of y.
Emission intensity after illuminating for 5000 hours relative to the emission intensity in the early stage of panel illumination that is assumed to be 100 is plotted along ordinate and the value of y is plotted along abscissa.
durability increases as the value of Y increases. This may be because, similarly to the case of the Eu dependency, ionic radius of the Sr ion is smaller than that of the Ba ion that is substituted thereby, and therefore bond distance between Eu and oxygen increases as the value of y increases, resulting in increasing bond energy.
Fig. 19 shows y dependency of relative emission intensity of the phosphor material having composition of Ba 0.95 - y) Sr y MgAl 10 O 17 :EU 0.05 after firing at 520°C and then firing again at 460°C in air.
the blue phosphor Ba 1-x MgAl 10 O 17 : Eu x of the prior art has such a problem that the durability decreases as the value of x is decreased for the purpose of improving the heat resistance, and a range of x from 0.1 to 0.15 has been used for this reason.
a phosphor material that is better in both heat resistance and durability than the conventional phosphor can be obtained by setting the Eu content x in a range from 0.08 to 0.01 and Sr content y in a range of 0.2 to 0.01 or lower in the phosphor material including Sr represented by Ba (1-x-y) Sr y MgAl 10 O 17 : Eu x .
Heat resistance improves further when the value of x is in a range from 0.02 to 0.075 inclusive, and the best result is achieved within a range from 0.03 to 0.06 inclusive.
Comprehensive evaluation of heat resistance and durability is better in a range of y from 0.02 to 0.15 inclusive, and best in a range of y from 0.02 to 0.1 inclusive.
the value of x+y is preferably in a range from 0.05 to 0.2 inclusive and most preferably in a range from 0.09 to 0.15 inclusive when these effects are taken into consideration.
the phosphor materials of different colors used in the fifth embodiment are made as described below.
the blue phosphor material is made by, first, mixing the predetermined quantities of the raw materials of barium carbonate (BaCO 3 ), magnesium carbonate (MgCO 3 ), aluminum oxide ( ⁇ -Al 2 O 3 ) , strontium carbonate (SrCO 3 ) and europium oxide (Eu 2 O 3 ) .
the mixture is mixed with a proper amount of flux (AlF 2 , BaCl 2 ) in a ball mill and the mixture is fired in a weakly reducing atmosphere (H 2 , N 2 ) at a temperature in a range from 1400 to 1650°C for a predetermined period of time (for example, 0.5 hours).
the red phosphor material is made by mixing the raw materials of yttrium hydroxide Y 2 (OH) 3 and boric acid (H 3 BO 3 ) in a proportion of 1: 1 by the numbers of atoms of Y and B. Then a predetermined amount of europium oxide (Eu 2 O 3 ) is added to the mixture, which is mixed with a proper amount of flux in a ball mill and fired at a temperature in a range from 1200 to 1450°C in air for a predetermined period of time (for example, one hour) .
Eu 2 O 3 europium oxide
the green phosphor material is made by mixing the raw materials of zinc oxide (ZnO) and silicon oxide (SiO 2 ) in a proportion of 2: 1 by the numbers of atoms of Zn and Si. Then a predetermined amount of manganese oxide (Mn 2 O 3 ) is added to the mixture and then mixed in a ball mill. The mixture is fired at a temperature in a range from 1200 to 1350°C in air for a predetermined period of time (for example, 0.5 hours).
the plasma display panels Nos. 501 through 504 shown in Table 10 are the plasma display panels of this example produced according to the fifth embodiment, while changing the values of x and y in Ba (1-x-y) Sr y MgAl 10 O 17 : Eu x of the blue phosphor.
the plasma display panels of samples Nos. 505 and 506 are the plasma display panels of Comparative Examples.
Luminance of the plasma display panels was measured under electric discharge conditions of 150V for. discharge holding voltage and 30kHz for frequency.
Luminance shown in the table gives the value of luminance when the signals of different colors were controlled to achieve color temperature of 9500 degrees for white display.
the phosphor layer of the plasma display panel uses much of phosphor materials that have such composition as a metal element that constitutes the base material is partially substituted with an activating agent.
a metal element that constitutes the base material is partially substituted with an activating agent.
BaMgAl 10 O 17 Eu 2+
Ba atoms are substituted by Eu 2+ ions.
the blue phosphor material of this type has been used in the prior art, as described previously, by setting the substitution ratio of Ba atoms by Eu 2+ ions to about 10 to 10 atomic %, supposedly for the following reason.
the phosphor layer is formed basically in such a process as the phosphor particles mixed with a binder is applied and then fired at about 500°C thereby removing the binder.
the front panel and the back panel are sealed to each other after forming the phosphor layer, by firing the panels at a temperature normally around 400°C. This means that the phosphor of the phosphor layer is subjected to firing twice.
the firing in the sealing process is carried out at a temperature significantly lower than the firing for forming the phosphor layer (around 500°C), it has been believed in the prior art that the firing for sealing does not affect the phosphor material significantly. The inventor of the present application found, however, that the second firing has substantial influence on the emission intensity of the phosphor layer.
the plasma display panel of the sixth embodiment of the present invention will be described below.
Fig. 21 is a schematic sectional view of an AC discharge type plasma display panel according to the sixth embodiment. While Fig. 21 shows only one cell, the plasma display panel comprises a number of cells that emit red, green and blue light being arranged thereon.
the plasma display panel of the sixth embodiment has a constitution similar to that of the second embodiment, except that the phosphor layers 219 of the second embodiment are replaced by phosphor layers 619 that include phosphor materials having predetermined composition.
the plasma display panel of the sixth embodiment being constituted by using the phosphor layers 619 that include the phosphor materials of the predetermined composition which will be described in detail later, has various excellent features to be described later.
the phosphor layers 619 are formed by continuously spouting the phosphor ink from the nozzles while scanning thereby applying the phosphor ink and firing the ink, similarly to the second embodiment. (Phosphor material and phosphor ink of the sixth embodiment and application thereof)
YBO 3 Eu 3+ and (Y x Gd 1-x )BO 3 : Eu 3+ , for example, may be used as the red phosphor material.
YBO 3 : Eu 3+ has such a structure that Y atoms that constitute the matrix of YBO 3 are substituted by Eu 3+
(Y x Gd 1-x ) BO 3 : Eu 3+ has such a structure that Y atoms and Gd atoms that constitute the matrix of (Y x Gd 1-x )BO 3 : Eu 3+ are substituted by Eu 3+ .
Zn 2 SiO 4 : Mn 2+ and BaAl 12 O 19 : Mn 2+ may be used as the green phosphor material.
Zn 2 SiO 4 Mn 2+ has such a structure that Zn atoms that constitute the matrix of Zn 2 SiO 4 are substituted by Mn 2+
BaAl 12 O 19 Mn 2+ has such a structure that Ba atoms that constitute the matrix of BaAl 12 O 19 are substituted by Mn 2+ .
red and green phosphor materials that are commonly used may be used without modification for the plasma display panel of the sixth embodiment.
the material represented by BaMgAl 10 O 17 : Eu 2+ is used. While a phosphor material wherein about 10 to 15% of the Ba atoms that constitute the matrix of BaMgAl 10 O 17 are substituted by Eu 2+ has been used in the plasma display panels, this embodiment employs a phosphor material wherein substitution ratio of Ba atoms by Eu 2+ ions is set within 8 atomic %, lower than the prior art.
red, green and blue phosphor material powders are used in the form of particles having average particle size in a range from 1 to 7 ⁇ m.
ethylcellulose or acrylic resin 0.1 to 10% by weight of ink
terpineol C 10 H 18 O
high polymers such as PMMA and polyvinyl alcohol may be used as the binder
organic solvent such as diethylene glycol methyl ether or water may also be used as the solvent.
the back glass substrate 15 is put in a furnace and fired at a temperature around 500°C for 10 to 20 minutes.
the organic binder included in the phosphor ink or fat included in the sheet is burned out in this firing process, thereby forming the phosphor layer 619 comprising the phosphor particles bonded in the form of film.
the phosphor is applied in the process described above by spouting the phosphor ink from the nozzles while scanning, the phosphor may also be applied by screen printing of phosphor paste.
the phosphor may also be applied by such a process as photosensitive resin sheets that contain phosphor materials of different colors are attached to the back glass substrate 15 on the side where the barrier ribs 18 are formed, whereon a pattern is formed by photolithography and development thereby removing unnecessary portions.
the phosphor materials of different colors described above can be made, for example, as follows.
the raw materials of barium carbonate (BaCO 3 ), magnesium carbonate (MgCO 3 ) , aluminum oxide ( ⁇ -Al 2 O 3 ) and europium oxide (Eu 2 O 3 ) are mixed so that molar ratio of the sum of Ba and Eu to Mf and Al is 1: 1: 10.
Molar ratio of Mg and Eu is determined according to the desired substitution ratio of Ba atoms by Eu 2+ ions.
molar ratio of Mg and Eu becomes 92: 8. Accordingly, molar ratio of barium carbonate, magnesium carbonate, aluminum oxide and europium oxide is set to 92: 4: 100: 500.
the mixture is mixed with a proper amount of flux (AlF 2 , BaCl 2 ) in a ball mill and the mixture is fired in a weakly reducing atmosphere (H 2 , N 2 ) at a temperature in a range from 1400 to 1650°C for a predetermined period of time (for example, 0.5 hours), thereby to obtain the BaMgAl 10 O 17 : Eu 2+ particles of the predetermined substitution ratio by Eu 2+ ions.
a proper amount of flux AlF 2 , BaCl 2
H 2 , N 2 a weakly reducing atmosphere
the raw materials of yttrium hydroxide Y 2 (OH) 3 , boric acid (H 3 BO 3 ) and europium oxide (Eu 2 O 3 ) are mixed in molar ratio of 1: 1 for the sum of Y and Eu to B.
Molar ratio of Y to Eu is determined according to the desired substitution ratio of Y atoms by Eu 3+ ions.
the mixture is mixed with a proper amount of flux in a ball mill and the mixture is fired in air at a temperature in a range from 1200 to 1450°C for a predetermined period of time (for example, 1 hour), thereby to obtain the YBO 3 : Eu 3+ particles of the predetermined substitution ratio by Eu 3+ ions.
the raw materials of zinc oxide (ZnO), silicon oxide (SiO 2 ) and manganese oxide (Mn 2 O 3 ) are mixed in molar ratio of 2: 1 for the sum of Zn and Mn to Si.
Molar ratio of Zn to Mn is determined according to the desired substitution ratio of Zn atoms by Mn 2+ ions.
the mixture is mixed in a ball mill and fired in air at a temperature in a range from 1200 to 1350°C for a predetermined period of time (for example, 0.5 hours), thereby to obtain the Zn 2 SiO 4 : Mn 2+ particles of the predetermined substitution ratio by Mn 2+ ions.
the plasma display panel of the sixth example was produced according to the sixth embodiment.
Zn 2 SiO 4 Mn 2+ (content of Mn is 2.3 weight %) was used for the green phosphor material and YBO 3 : Eu 3+ (substitution ratio by Eu 2+ ions 0.1) was used for the red phosphor.
BaMgAl 10 O 17 : Eu 2+ was used for the blue phosphor, where substitution ratio of Ba atoms by Eu 2+ ions was set to 0.5, 2.0, 5.0, and 8.0 atomic % for Nos. 601 through 604, respectively, as shown.in Table 11.
composition of the blue phosphor is given as Ba 1-x MgAl 10 O 17 : EU x which represents the same phosphor that is represented by BaMgAl 10 O 17 : Eu 2+ , while the substitution ratio of Ba atoms in the base material by Eu 2+ ions is represented in the formula by x.
Average particle size was set to about 3 ⁇ m for the phosphor material powders of all colors. Firing for the formation of the phosphor layer was carried out at 520°C for 10 minutes and firing for the lamination of the panels was carried out at 460°C for 10 minutes. Thickness of the phosphor layer was set to 20 ⁇ m and discharge gas pressure was set to 500 Torr.
Color temperature non-adjusted luminance and color temperature-adjusted luminance were measured on the plasma display panels of this example and Comparative Example produced as described above.
the color temperature non-adjusted luminance refers to the luminance of white display with the same signals given for all colors (namely having the discharge spaces of the three colors emit equivalent ultraviolet rays), and color temperature-adjusted luminance refers to the luminance when the signals of different colors are adjusted to achieve color temperature of 9500 degrees in white display.
Luminance was measured under electric discharge conditions of 150 V for discharge holding voltage and 30kHz for frequency. The measurements results are shown in Table 11.
the color temperature-adjusted luminance is measured while giving consideration to the fact that improving the picture quality of the plasma display panel requires it to take white balance. Higher luminance can be achieved while maintaining good picture quality, as the color temperature-adjusted luminance is increased,
the blue phosphor material has, in general, lower luminance than the phosphor materials of other the colors, emitting the light of all colors with the same signal results in a color temperature of around 6000 degrees and good picture quality cannot be obtained.
Phosphor pastes were made by using the phosphor materials made as described above and applied to substrates that were then fired at 520°C in air for 10 minutes thereby forming phosphor layers. The phosphor layers thus formed were further fired at 460°C in air for 10 minutes.
Luminance and emission intensity of these phosphor layers were measured by irradiating the phosphor layer with ultraviolet rays emitted by a UV lamp before being fired at 520°C (pre-firing) , after being fired at 520°C (after first firing) and after being fired at 460°C (after second firing).
Luminance was measured with a luminance meter. Intensity was determined by measuring the emission spectrum from the phosphor layer with a spectrophotometer, calculating y value of chromaticity from the measurement and calculating the emission intensity from the y value of chromaticity and the measured luminance (luminance/y value of chromaticity).
Fig. 22A, 22B show the results of measurement described above, with Fig. 22A showing the relation between the value of x and relative luminance and Fig. 22B showing the relation between the value of x and relative emission intensity.
Fig. 22A, 22B solid lines represent the characteristic before firing, dashed lines represent the characteristic after the first firing, and alternate dot and dash lines represent the characteristic after the second firing.
luminance reaches a peak at a point where the value of x is a little larger than 0.1 and maintains high level even when the value of x decreases significantly.
the firing process has opposite effects on the emission intensity depending on whether the value of x is below 0.08 or greater than 0.08. That is, in the range of x greater than 0.08, emission intensity after firing is lower than that before firing.' In the range of x below 0.08, on the contrary, emission intensity becomes higher after firing than that before firing, and both the luminance and the emission intensity become higher after the second firing than after the first firing.
Fig. 22A, 22B show the results of measurements carried out up to the point after two firing steps; firing at 520°C followed by firing at 460°C. However, similar effects were also obtained from measurement made after third firing at 460°C following the two firing steps.
the phosphor represented by BaMgAl 10 O 17 : Eu 2+ is described as an example of blue phosphor that contains Eu 2+ ions as the activation agent.
the present invention is not limited to this configuration, and can also be applied to a case where BaMgAl 14 O 23 : Eu 2+ or Ba a Sr 1-a MgAl 10 O 17 : Eu 2+ is used as the blue phosphor.
Similar effects can be achieved also by setting the substitution ratio by Eu 2+ ions in the case of BaMgAl 14 O 23 : Eu 2+ and substitution ratio of Ba atoms and Sr atoms by Eu 2+ ions in the case of Ba a Sr 1-a MgAl 10 O 17 : Eu 2+ to 8 atomic % or lower (preferably in a range from 1 to 6 atomic %).
application of the blue phosphor material described in the sixth embodiment is not limited to the plasma display panel, and is applicable also to a fluorescent lamp, for example, with similar effects.
the present invention provides the phosphor material and the phosphor material powder having high emission intensity and high luminance, of which application to the plasma display panel makes it possible to provide high luminance and high definition plasma display panel.

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EP03020149A 1997-11-06 1998-11-05 Phosphormaterial und Plasma-Anzeigetafel Expired - Lifetime EP1375626B1 (de)

Applications Claiming Priority (16)

Application Number	Priority Date	Filing Date	Title
JP30418497		1997-11-06
JP9304184A JPH11144625A (ja)	1997-11-06	1997-11-06	プラズマディスプレイパネル及びその製造方法
JP33535397		1997-12-05
JP9335353A JPH11166178A (ja)	1997-12-05	1997-12-05	蛍光体材料，蛍光体膜およびプラズマディスプレイパネル
JP9347465A JPH11172241A (ja)	1997-12-17	1997-12-17	蛍光体材料，蛍光体膜およびプラズマディスプレイパネル
JP34746597		1997-12-17
JP14098		1998-01-05
JP14098		1998-01-05
JP05172298A JP3161409B2 (ja)	1998-03-04	1998-03-04	プラズマディスプレイパネル
JP5172298		1998-03-04
JP13298398A JP3185752B2 (ja)	1998-05-15	1998-05-15	蛍光体材料，蛍光体膜およびプラズマディスプレイパネル
JP13298398		1998-05-15
JP19300098		1998-07-08
JP19300098A JP3202964B2 (ja)	1998-01-05	1998-07-08	蛍光体材料、蛍光体膜およびプラズマディスプレイパネル
EP98951690A EP1030339B1 (de)	1997-11-06	1998-11-05	Lumineszenzmittel, pulverförmiges lumineszenzmittel, plasma-anzeigetafel und herstellungsverfahren dersleben
EP02019504A EP1267383B1 (de)	1997-11-06	1998-11-05	Plasma-Anzeigetafel und Herstellungsverfahren derselben

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EP02019503A Expired - Lifetime EP1261013B1 (de)	1997-11-06	1998-11-05	Lumineszenzmittel, pulverförmiges Lumineszenzmittel, Plasma-Anzeigetafel, und Herstellungsverfahren derselben
EP03020149A Expired - Lifetime EP1375626B1 (de)	1997-11-06	1998-11-05	Phosphormaterial und Plasma-Anzeigetafel
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EP02019503A Expired - Lifetime EP1261013B1 (de)	1997-11-06	1998-11-05	Lumineszenzmittel, pulverförmiges Lumineszenzmittel, Plasma-Anzeigetafel, und Herstellungsverfahren derselben

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JP3915458B2 (ja) *	2001-09-12	2007-05-16	松下電器産業株式会社	プラズマディスプレイ装置
JP4727093B2 (ja) *	2001-09-12	2011-07-20	パナソニック株式会社	プラズマディスプレイ装置
JP4042372B2 (ja) *	2001-09-12	2008-02-06	松下電器産業株式会社	蛍光体の製造方法
TWI290329B (en) *	2001-10-30	2007-11-21	Hitachi Ltd	Plasma display device, luminescent device and image and information display system using the same
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Publication number	Publication date
EP1375626A3 (de)	2004-02-18
US6667574B2 (en)	2003-12-23
EP1261013A1 (de)	2002-11-27
DE69824034D1 (de)	2004-06-24
DE69824034T2 (de)	2005-06-30
CN1475546A (zh)	2004-02-18
EP1267383A1 (de)	2002-12-18
EP1375626B1 (de)	2007-04-04
US20030107318A1 (en)	2003-06-12
CN1247736C (zh)	2006-03-29
US6614165B1 (en)	2003-09-02
EP1030339A1 (de)	2000-08-23
DE69837500T2 (de)	2007-12-13
DE69824053D1 (de)	2004-06-24
DE69836837D1 (de)	2007-02-15
EP1267383B1 (de)	2007-01-03
US6833672B2 (en)	2004-12-21
EP1030339A4 (de)	2001-03-14
US20030137234A1 (en)	2003-07-24
WO1999024999A1 (fr)	1999-05-20
DE69836837T2 (de)	2007-10-18
EP1030339B1 (de)	2004-05-19
CN1285081A (zh)	2001-02-21
DE69824053T2 (de)	2005-05-12
DE69837500D1 (de)	2007-05-16
CN1129946C (zh)	2003-12-03
EP1261013B1 (de)	2004-05-19

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